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Mr.RC-Cam

RCFS-V2: New FailSafe with Glitch Filtering.

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Lowest price scope on the planet that works well for hobby activities: http://www.jyetech.com/Products/LcdScope/eDSO062.php

Honestly, if you don't already have a scope then just shrug this issue off and continue using your workaround. So, the big question is: does the RCFS-V2 provide failsafe when your 2.4GHz R/C signal is lost? Most 2.4GHz receivers continue to send fake servo pulses, so RCFS-V2 will not recognize that the RF signal is missing. That means it won't work in such situations. That is why the RCFS-V2, and similar commercial products, are promoted for PPM installations only.

well i programmed it on my jr rx/tx combo and it worked fine.

what i noticed is that the hobby*ing rx when the tx is switched off the servo stays i the last positionit was, thats why i build the failsafe to throw the throttle to idle.

it's working fine on the 2.4ghz system, next will be a range test. though thinking the pulse to the servo is the same as that of the jr system ? will have to check the specs then.

thanks for the support. i will post the servo pulse from the 2.4ghz rx.

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well i programmed it on my jr rx/tx combo and it worked fine.

what i noticed is that the hobby*ing rx when the tx is switched off the servo stays i the last positionit was, thats why i build the failsafe to throw the throttle to idle.

it's working fine on the 2.4ghz system, next will be a range test. though thinking the pulse to the servo is the same as that of the jr system ? will have to check the specs then.

thanks for the support. i will post the servo pulse from the 2.4ghz rx.

just for your info , heres a link of the tx/rx i am using

http*://www.hobby*king.com/hobbyking/store/uh_viewItem.asp?idProduct=9042&Product_Name=Hobby_King_2.4Ghz_6Ch_Tx_&_Rx_%28Mode_2%29

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The RCFS-V2 is designed for PPM receivers; it would probably never kick into fail safe on a typical 2.4GHz R/C system.

i made on my rx/tx combo it is described as the mfgr calls "PPM/GFSK". GFSK, Gaussian Frequency Shift Keying , so the output to the servo should be standard.

the microcontroller used is http://www.ai-hk.cn/miconiclan/EM78P4589.pdf this.

what do you think

should i try the v2.1 firmware ?

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What matters is whether your RX still gives out servo pulses when the TX is off or not. Connect an analog servo to the channel you want to add failsafe to. Confirm it moves normally - always a good idea. Now turn off the TX, and try to turn the servo by hand. Does it hold its position? If not, then your RCFS will work. If it does, then your RX already has some basic failsafe in the form of holding the last received position, and you're out of luck because the RCFS will never be able to detect a loss of signal.

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What matters is whether your RX still gives out servo pulses when the TX is off or not. Connect an analog servo to the channel you want to add failsafe to. Confirm it moves normally - always a good idea. Now turn off the TX, and try to turn the servo by hand. Does it hold its position? If not, then your RCFS will work. If it does, then your RX already has some basic failsafe in the form of holding the last received position, and you're out of luck because the RCFS will never be able to detect a loss of signal.

i connected a analog servo to the throttle channel, i switched off the tx and the servo freezed at the last position, i then connected the rcfs in between and tested again . when i switched off the tx , rcfs quickly flashed the led and then the servo moved to the preset position.the led stay rock solid on.

does this mean the rx is sending a pulse to the servo and still the rcfs is going into failsafe.

i shall measure the rx servo pulses with my oscilloscope to see the difference between the hobbyking and jr sets

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If RCFS-V2 is going to the preset location when your turn off the Tx then you have confirmed that the receiver is no longer producing servo signals. Your test demonstrates that RCFS-V2 should work with your 2.4GHz system, which is not typical of the usual 2.4GHz systems.

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If RCFS-V2 is going to the preset location when your turn off the Tx then you have confirmed that the receiver is no longer producing servo signals. Your test demonstrates that RCFS-V2 should work with your 2.4GHz system, which is not typical of the usual 2.4GHz systems.

i should correct my observations,

when the hobbking tx is switched off , the red led on the rx and satellite switches off, the servo is without a signal as i managed to turn it with my fingers without problems. this confirm that rcfs works. on such unit.

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Hello. I just finished assembly of my RCFS-v2 (before I put it into heat shrink tube):

rcfsv2a.th.jpgrcfsv2b.th.jpg

5V LDO regulator is used because I have 5 cell(6V) receiver pack in my 1:8 nitro buggy. The failsafe works OK, used on throttle/brake servo and I set it to almost full brake when activated.

I have few remarks:

1. Low voltage detection works, however level is around 3.7-3.8V(and 4.2V when raising)what is a bit low for 5 cell pack(ideal low voltage level is 4.5-5.0V). Probably no way to solve it for 5 cell packs as 5V LDO keeps PIC supply voltage constant until battery voltage drops to 5V(nearly pack minimum voltage), then then PIC supply voltage starts to drop also. Until this point PIC don't know about battery voltage drop. Hope I explain it clearly.

2. I see different period than 20ms(50Hz) of output signal when failsafe is activated(missing pulses), I have measured 27ms(37Hz). However when failsafe is activated due to low voltage(input pulses are still present), output signal period is correct 50Hz. If I cut input pulses at this time, period of output pulses changes again to 37Hz.

I don't know if different period is intention(and why at low voltage detection is OK), fortunately my servo accepts 37Hz framerate also. For sure I have tested to re-program PICs(osccal is surely kept), still same, I also programmed second PIC on different professional programmer, again same behaviour.

First trace(tek00078): output pulsed with correct input(1.41ms), failsafe not activated. Output period 50Hz

Second trace(tek00079): output pulses with missing input, failsafe activated(set to 1.68ms). Output period 37Hz

Third trace(tek00080): output pulses when input pulses are present, failsafe activated due to low voltage. Output period 50Hz

Fourth trace(tek00081): output pulses with missing input pulses and low voltage, failsafe activated. Output period 37Hz

tek00078.th.pngtek00079.th.pngtek00080.th.pngtek00081.th.png

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1. The Low Voltage feature was characterized for a 4-cell pack. I don't have a solution for your higher battery voltage, but try sourcing R2 from the unregulated battery voltage and experiment with slightly different values at D1.

2. When a valid receiver/servo pulse is present the output frame rate is synchronized to the receiver's frame rate. If the receiver pulse is invalid for any reason then a fake frame rate is created. The provided ~37Hz fake frame rate is fine.

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Thanks Mr.RC-Cam!

It is not problem for me as I cannot use failsafe low voltage detection on 6V pack, I understand circuit is intended for 4 cells. Anyway I use simple battery low voltage indicator(flashes bright LED at low voltage) it has truly negligible consumption(when flashing as well) therefore I keep it connected permanently to my receiver pack.

Good to know about different framerate. I suspected something is wrong, but now it is clear for me.

Thanks again for your great projects!

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Mr. RC-CAM,

I wonder if you would be willing to modify the code slightly to your RCFS-V2?

I think you will find this would be an added enhancement and useful to many users.

In a parachute project I made, I wanted to remotely turn the power off to the receiver and all by simply turning off the TX. I used a Berg RX because it would go into idle mode with the loss of signal. Then I used an LM555 as a missing pulse detector. After a timed delay, it would remove the power to a latching relay and thus remove power to my project. It worked well most of the time, except that sometimes the Berg RX would send out a stray pulse and this would retrigger the LM555 before it timed out, and so it wasn’t 100% reliable.

You have an unused pin on the PIC12F683 (GP2/AN2). Could you modify the code so that when the servo signal is normal, this output goes high? And then, when the PIC goes into failsafe, after a delay of ten seconds or so, the output would go low? (the delay is important, because you wouldn’t want power removed prematurely).

I can also see where this could come in very handy for guys that like to drive boats. When and if a boat is stalled or capsized in the middle of the pond, you could turn power off by simply turning off the TX, and then avoiding possible damage to your electronics when they get wet.

A reset button and a MOSFET make for a great latching relay.

Whatcha think?

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I receive an endless number of requests for customizing the various RC-CAM projects. Unfortunately I'm overloaded with things on my own honey-do list so I am not able to create customize versions for others.

One of the goals of the RC-CAM site is to show how versatile modern microcontrollers are so that other DiY'ers will be interested in creating their own designs. It doesn't have to be a PIC (there are easier to use chips out there). For example, the Arduino seems to be a popular chip for DiY builders and there are many public code examples to help get started.

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Does RCFS v2 work with Turnigy 9x 8 and 6 channel receivers? As you know those receivers don't have failsafe, and it would be cool to add that feature on the throttle channel,...Maybe it could be also used with APM2 so it initiates RTH? What are your thoughts on that?

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I could be wrong, but I think those rx's turn off their servo signals when the R/C signal is lost. If true, then that is good news for RCFSV2. I think it might work, but don't know for sure.

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That would be bad news. But you should check your Rx to see what it does and confirm it.

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Just built two of these with low voltage detection and I am unable to program any of the 3 modes. LED flashes on power up when holding the button and goes out when released but then it won't accept any of the 3 modes. Pressing the button lights the LED but that's it. Any idea what the problem is?

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Any idea what the problem is?

Some thoughts:

1. Is the R/C system turned on? RCFS programming mode will abort if a valid servo pulse is not being received from the R/C receiver.

BTW, servo pulse frame-rate must be traditional 50Hz (38 to 62 Hz is allowed). If you have a o-scope then confirm your R/C signal satisfies this requirement.

2. Low voltage detection problem? While debugging I suggest you disable the low voltage circuitry.

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Yep, system is on, servo operates correctly thru the Fail Safe via the TX. When the TX is switched off, LED flashes rapidly and lights steady, immediately goes out when TX is switched on. I have bypassed the low voltage detection with a jumper from pin3 to GND, no change.

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All your observations seem reasonable.

As a test, follow the steps below and provide feedback. The RCFS will be set to Hold mode with Impulse Filter data averaging.

1. Turn on R/C transmitter. Remove power from receiver & servos.
    Press and HOLD the button on RCFS. Apply receiver power.
   The LED should flash. It should continue to flash until the button is released, then turn off. Is this what you see?

2. Next, press the button TWO times to enable the hold mode. This must be done within five seconds of entering programming mode. Did you see the LED blink after each press?

3. After the second press wait five seconds. At the end of the five second wait the LED should change to a continuous rapid flash. Do you see this?

4. As soon as you see the flashing LED, press the button once. This enables the filter mode. The LED will acknowledge by a single LED blink and programming mode is exited.

5. R/C system operation should be normal at this point. Confirm the servo operates correctly when the radio's stick is moved.

6. Press RCFS button once. It will blink a pattern that reports its configuration. What do you see?

During normal operation (Tx on), pressing the PB Switch will blink out the active Failsafe mode.
  1-Blink = Idle mode (servo signal turns off)
  2-Blink = Hold mode
  3-Blink = Fixed Position mode.
After a short delay (about two seconds), the LED will blink one more time if the Impulse Filter (averaging) is turned on.

 

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All good up to step #3. The LED never gets to rapid flash. I don't think it ever enters program mode. At any time after power up, I can hold the button and the LED will slow blink, just as it does when holding the button and then powering up.

 

Edited by JackMan

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I don't think it ever enters program mode.

That might be the reason. The R/C servo signal must be present when RCFS boots up. If the servo signal is delayed when the receiver is turned on then RCFS will ignore programming mode.

Try the test again. But disconnect RCFS from the receiver before starting the test. After the receiver is powered up and confirmed working, plug in RCFS while holding the programming button. Confirm the flashing LED while the button is held/pressed. Then proceed to step 2 in my previous post to see if the problem is resolved.

BTW, what brand/model receiver are you using? It should be an old analog design with simple shift register decoding (no microcontrollers) that uses 50Hz framerates. That's what was commonly available in 2005 when this project was created. AKA, the good old days.

Also, if you have an oScope then please post a screenshot of the servo pulse waveform.

 

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You are welcome. Thanks for letting me know you got it working.

 

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